Wireless communication networks, such as cellular telephone communication networks, are commonplace. Wireless communication networks may comply with one or more standards or recommendations, such as the Global System for Mobile communication (GSM) recommendations. A system operating according to the GSM recommendations will typically include a switching system (SS), a base station system (BSS) and an operation and support system (OSS).
The base station system provides all of the radio-related functions, and the BSS typically includes one or more base station controllers (BSCs) and a plurality of base transceiver stations (BTSs). The base station controller provides all the control functions and physical links between the switching system and the base transceiver station. The base station controller is a high-capacity switch that provides functions such as handover, cell configuration, and control of radio frequency (RF) power levels in the base transceiver stations.
The BTS handles the radio interface to the mobile station (MS). The mobile station is the subscriber equipment used to access the wireless communication network. The base transceiver station includes the radio equipment (transceivers, antennas, amplifiers, etc.) needed to service each cell in the network. A group of base transceiver stations is controlled by a base station controller.
The operation and support system is the functional entity from which the network operator monitors and controls the system. The purpose of the OSS is to provide centralized, regional and localized operation and maintenance activities required for wireless communication network operation. For example, the operation and support system provides a network overview and supports maintenance activities of different operation and maintenance organizations. The operation and support system may include an operation and maintenance center (OMC) coupling all the equipment in the wireless communication network.
The switching system is responsible for performing call processing and subscriber related functions. The switching system includes: the home location register (HLR), the mobile services switching center (MSC), visitor location register (VLR), authentication center (AUC) and equipment identity register (EIR).
In General Packet Radio Service (GPRS) communication networks, for example, it may be necessary for the BTS to communicate with multiple mobile stations simultaneously. To do this, the BTS uses a single communication channel or resource that may be monitored by each MS operating in the communication network. For a GPRS communication network utilizing time division multiple access (TDMA) protocol, this single communication channel is a single block or on a single timeslot (a packet). Some of the reasons that necessitate the need to reach multiple mobile stations with a single packet include point to multipoint transfers (during which several mobile stations may be the intended recipient of a given packet, broadcast transfers (where all mobile stations in a specific geographic region need to be reached, and normal operation using Dynamic Allocation for radio resource scheduling. The European Telecommunications Standards Institute (ETSI) standards defining GPRS outline three different types of access mechanisms: Fixed Allocation, Dynamic Allocation, and Extended Dynamic Allocation.
Fixed Allocation is a mechanism by which the BSS pre-determines a schedule for each MS needing to transmit or receive data and communicates this scheduling information to each impacted MS. Periodically this information is updated to allow changes in the schedule to accommodate mobile stations that have completed transfers, new mobile stations which are waiting to transfer, and retransmission of corrupted blocks for existing transfers. This scheduling mechanism has inefficiencies. When a mobile station suddenly stops sending data without warning, the remainder of that mobile station's allocation is wasted as the scheduler cannot retract the blocks already allocated to that mobile station.
Dynamic Allocation and Extended Dynamic Allocation are mechanisms by which the GPRS network indicates to a given a mobile station that during the next occurrence of the timeslot in the uplink direction, the indicated mobile station is to transmit an uplink packet. The packet data needs of all of the mobile stations in the cell are assessed every block period and this activity is repeated. At the beginning of each resource request made by the mobile station, a code is sent to the mobile station that indicates which address (Uplink State Flag) will be used on the given timeslot for that mobile station. From this point on the mobile station must listen to the downlink packets for its Uplink State Flag value to appear. In the Dynamic Allocation cases, the GPRS network communicates with at least two mobile stations at the same time. The information indicating which mobile station has been scheduled to transmit on the next uplink block is contained in a group of bits (Uplink State Flags) in each downlink message that also contains data payload for a potentially different mobile station.
In all of the cases in which multiple mobile stations are receiving the same downlink blocks, the GPRS network must always transmit downlink blocks at a transmit level high enough to reach all intended mobile stations. This can result in a higher than necessary transmit level in the network. Transmitting with higher than necessary power increases interference within the communication network. It also increases the dynamic range with which the mobile stations must be designed to cope.
Thus, there is a need for a method and apparatus for scheduling communication services in a wireless communication network.